JP2012047959A - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that suppresses the occurrence of a streaky image defect in a electrophotographic photoreceptor axis direction.SOLUTION: An outermost surface layer of a photoreceptor comprises: a styryl charge transport material with a specific structure; a polycarbonate binary copolymer resin having a specific structural unit; a phenol compound with a specific structure; and a diamine compound with a specific structure.

Description

  The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an image forming apparatus.

  In a conventional electrophotographic image forming apparatus, a toner image formed on the surface of an electrophotographic photosensitive member is transferred to a transfer target through charging, exposure, development, and transfer processes.

  For example, Patent Documents 1 and 2 disclose a method of reducing the surface energy of the surface layer of the photoreceptor by dispersing fluorine resin particles in the surface layer, and Patent Document 3 discloses conductive metal particles on the surface layer. And a method of containing a fluororesin has been proposed.

  Patent Document 4 proposes that the surface of the electrophotographic photosensitive member can be reduced by charging the surface of the electrophotographic photosensitive member by applying only a DC voltage to a contact-type charging member.

JP-A-63-221355 JP-A-6-337536 JP-A-6-250460 JP-A-2005-107366

  The object of the present invention is to suppress the occurrence of streak-like image defects in the axial direction of the electrophotographic photosensitive member in an intermediate gradation image, as compared with a case where the outermost surface layer configured to contain the following specific compound is not provided. An electrophotographic photoreceptor is provided.

The above problem is solved by the following means. That is,
The invention according to claim 1
Having at least a conductive substrate and a photosensitive layer disposed on the conductive substrate,
The outermost surface layer includes at least a charge transport material represented by the following general formula (1), a structural unit represented by the following general formula (2), and a structural unit represented by the following general formula (3). An electrophotographic photoreceptor comprising a polycarbonate resin, a compound represented by the following general formula (4), and a compound represented by the following general formula (5).

(In General Formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 carbon atom. It represents an alkoxy group having 20 or less or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure. m represents 0, 1 or 2 each independently.)

(In General Formula (2), R ⁷ and R ⁸ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or 6 carbon atoms. Represents an aryl group of 12 or less.)
(In General Formula (3), R ⁹ and R ¹⁰ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or 6 carbon atoms. Represents an aryl group having at least 12 but X is —CR ¹¹ R ¹² — (wherein R ¹¹ and R ¹² are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or Represents an aryl group having 6 to 12 carbon atoms), a 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, —O—, -S -, - SO-, or -SO ₂ - represents a).

(In General Formula (4), R ²¹ , R ²² , and R ²³ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.)
(In General Formula (5), R ³¹ and R ³² each independently represents an alkyl group having 1 to 20 carbon atoms. R ³³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. R ³⁴ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aromatic group, R ³⁵ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, R ³⁶ And R ³⁷ each independently represents an alkyl group having 1 to 20 carbon atoms.

The invention according to claim 2
The electrophotographic photosensitive member according to claim 1, wherein the outermost surface layer has a thickness of 25 μm or more.

The invention according to claim 3
The electrophotographic photosensitive member according to claim 1 or 2,
Contact-type charging means for charging the electrophotographic photosensitive member by application of a DC voltage; and
Comprising at least
A process cartridge that is detachable from the image forming apparatus.

The invention according to claim 4
The process cartridge according to claim 3, wherein the process cartridge does not have a charge removing unit for discharging charges on the electrophotographic photosensitive member after the toner image is transferred to the transfer target and before the electrophotographic photosensitive member is charged.

The invention according to claim 5
The electrophotographic photosensitive member according to claim 1 or 2,
Contact-type charging means for charging the electrophotographic photosensitive member by application of a DC voltage; and
Electrostatic latent image forming means for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image; and
Toner image forming means for developing the electrostatic latent image formed on the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring a toner image formed on the electrophotographic photosensitive member to a transfer target;
Fixing means for fixing the toner image transferred to the transfer target;
An image forming apparatus.

The invention according to claim 6
6. The image formation according to claim 5, wherein the toner image is not provided with a discharging unit for discharging charges on the electrophotographic photosensitive member after the toner image is transferred to the transfer target and before the electrophotographic photosensitive member is charged. apparatus.

According to the first aspect of the present invention, compared to the case where the outermost surface layer configured to contain the specific compound is not provided, in the halftone image, the stripe-like image defect in the electrophotographic photosensitive member axial direction is eliminated. Occurrence is suppressed.
According to the second aspect of the present invention, even if an outermost surface layer having a thickness in the above range, in which a streak-like image defect in the axial direction of the electrophotographic photosensitive member easily occurs in an intermediate gradation image, The generation of the streak-like image defect is suppressed as compared with the case where the outermost surface layer including the compound is not provided.
According to the inventions according to claims 3 and 5, compared with the case where an electrophotographic photoreceptor not having a charge transport layer comprising the specific compound is provided, an electrophotographic photoreceptor is provided in an intermediate gradation image. Occurrence of streak-like image defects in the axial direction is suppressed.
According to the inventions according to claims 4 and 6, even in a configuration in which a streak-like image defect in the electrophotographic photosensitive member axial direction is likely to occur in an intermediate gradation image, and there is no neutralization means, In comparison with the case where an electrophotographic photoreceptor having no charge transport layer composed of a compound is provided, the occurrence of streak-like image defects in the axial direction of the electrophotographic photoreceptor is suppressed in an intermediate gradation image.

1 is a schematic cross-sectional view showing an electrophotographic photosensitive member according to the present embodiment. It is a schematic sectional drawing which shows the electrophotographic photoreceptor which concerns on this other embodiment. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the image forming apparatus which concerns on other this embodiment.

  Embodiments that are examples of the present invention will be described below.

[Electrophotographic photoreceptor]
The electrophotographic photoreceptor according to the exemplary embodiment includes a conductive substrate and a photosensitive layer provided on the conductive substrate. The outermost surface layer of the photoconductor is represented by at least a charge transport material represented by the following general formula (1), a structural unit represented by the following general formula (2), and the following general formula (3). A polycarbonate resin comprising a structural unit, a compound represented by the following general formula (4), and a compound represented by the following general formula (5).
The outermost surface layer means a layer arranged on the side farthest from the conductive substrate. When the photosensitive layer is a function-separated type photosensitive layer having a charge generation layer and a charge transport layer in this order, the charge generation is performed. When the layer corresponds to the outermost surface layer and the photosensitive layer is a single layer type photosensitive layer, the single layer type photosensitive layer corresponds to the outermost surface layer.

  Here, conventionally, for the purpose of reducing the wear amount (scraping amount) of the outermost surface layer of the electrophotographic photosensitive member, a contact-type charging means for charging the electrophotographic photosensitive member by applying a DC voltage has been adopted. Yes. This contact-type charging means simplifies the configuration of the power supply and harness (bundling a plurality of electric wires for the purpose of power supply and signal communication), thereby reducing the overall cost of the apparatus. In recent years, it has been actively adopted because it is reduced.

However, if this contact-type charging means is adopted, abnormal discharge is likely to occur. Therefore, a streak-like image defect in the axial direction of the electrophotographic photoreceptor occurs in an intermediate gradation image (so-called halftone image). It has been found that it becomes easier.
In particular, it has also been found that this phenomenon occurs remarkably when the outermost surface layer of the electrophotographic photosensitive member is thick or when no static eliminating means is employed.

  Therefore, in the electrophotographic photosensitive member according to the present embodiment, the occurrence of streak-like image defects in the axial direction of the electrophotographic photosensitive member is suppressed in the intermediate gradation image (so-called halftone image) by adopting the above configuration. The

The charge transport material represented by the general formula (1) and the polycarbonate resin including the structural units represented by the general formulas (2) and (3) are mixed to form the outermost surface layer. By doing so, it is thought that it has the function which forms the intermolecular interaction of polycarbonate resin and improves the intensity | strength of a layer.
On the other hand, it is speculated that the charging failure is caused by radicals in the oxidized state on the surface of the electrophotographic photosensitive member or the outermost surface layer, which obstruct charging uniformity, and are represented by the general formulas (4) and (5). When used in combination with a compound, the compound is considered to have a function of eliminating these radicals. In addition, the compound relatively increases the residual potential to form a charge bias (charge trap) in the outermost surface layer of the electrophotographic photosensitive member. However, even if abnormal discharge occurs, the charge bias (charge) It is thought that the trap) has a function of discharging (leaking) at the abnormally charged portion on the surface and making the charge uniform.
However, in this embodiment, the reason is not clear. However, when the outermost surface layer is formed by combining the above-described materials having the respective functions, an electrophotographic image is obtained in an intermediate gradation image (so-called halftone image). Occurrence of streak-like image defects in the axial direction of the photoreceptor is suppressed.

  In the electrophotographic photoreceptor according to the exemplary embodiment, even when the outermost surface layer has a thickness of, for example, 25 μm (preferably 18 μm to 40 μm, more preferably 24 μm to 30 μm), Generation of streak-like image defects in the axial direction of the electrophotographic photosensitive member is suppressed in an intermediate gradation image (so-called halftone image).

Then, by mounting the electrophotographic photosensitive member according to this embodiment on a process cartridge and an image forming apparatus provided with a contact-type charging unit that charges the electrophotographic photosensitive member by applying a DC voltage, Generation of image defects is suppressed.
In addition, in particular, a charge eliminating unit that easily causes the streak-like image defect (after the transfer of the toner image to the transfer target and before the charging of the electrophotographic photosensitive member, the charge on the electrophotographic photosensitive member is discharged. Even in a process cartridge and an image forming apparatus that do not have a charge eliminating means), the occurrence of the streak-like image defect is suppressed by mounting the electrophotographic photosensitive member according to this embodiment.

The details of the electrophotographic photosensitive member according to this embodiment will be described below.
FIG. 1 is a schematic cross-sectional view showing the electrophotographic photoreceptor according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing an electrophotographic photoreceptor according to another embodiment.

An electrophotographic photoreceptor 10A shown in FIG. 1 is, for example, a so-called function-separated photoreceptor (or a laminated photoreceptor). An undercoat layer 1 is provided on a conductive substrate 4, and a charge generation layer 2 is formed thereon. And a structure in which the charge transport layer 3 is sequentially formed. In the electrophotographic photoreceptor 10A, the charge generation layer 2 and the charge transport layer 3 constitute a photosensitive layer.
In the electrophotographic photoreceptor 10 </ b> A shown in FIG. 1, the charge transport layer 3 is the outermost surface layer disposed on the side farthest from the conductive substrate 4.

An electrophotographic photoreceptor 10B shown in FIG. 2 contains, for example, a charge generation material and a charge transport material in the same layer (single layer type photosensitive layer 6 (charge generation / charge transport layer)).
Specifically, the electrophotographic photoreceptor 10B shown in FIG. 2 has a structure in which the undercoat layer 1 is provided on the conductive substrate 4 and the single-layer type photosensitive layer 6 is formed thereon. .
In the electrophotographic photoreceptor 10 </ b> B shown in FIG. 2, the single-layer type photosensitive layer 6 is the outermost surface layer disposed on the side farthest from the conductive substrate 4.

  In the electrophotographic photoreceptor shown in FIGS. 1 and 2, the undercoat layer 1 may or may not be provided.

  Hereinafter, each element in the electrophotographic photosensitive member will be described. Hereinafter, description will be made with the reference numerals omitted.

First, the conductive substrate will be described. “Conductivity” means, for example, a volume resistivity of 10 ¹³ Ω · cm or less.
Any conductive substrate may be used as long as it is conventionally used. For example, thin films (eg, metals such as aluminum, nickel, chromium, stainless steel, and films of aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, indium tin oxide (ITO), etc.) And a plastic film coated or impregnated with a conductivity-imparting agent, a plastic film coated or impregnated with a conductivity-imparting agent, and the like. The shape of the conductive substrate is not limited to a cylindrical shape, and may be a sheet shape or a plate shape.

  When a metal pipe is used as the conductive substrate, the surface may be left as it is, and treatments such as mirror cutting, etching, anodizing, rough cutting, centerless grinding, sand blasting, and wet honing have been performed in advance. Also good.

Next, the undercoat layer will be described.
The undercoat layer is provided as necessary for the purpose of preventing light reflection on the surface of the conductive substrate and preventing inflow of unnecessary carriers from the conductive substrate to the photosensitive layer.

The undercoat layer includes, for example, a binder resin and, if necessary, other additives.
As the binder resin contained in the undercoat layer, acetal resins such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, Known polymer resin compounds such as polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, and charge transporting group Examples thereof include charge transporting resins having a conductive resin such as polyaniline. Among these, resins that are insoluble in the upper coating solvent are preferably used, and phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, epoxy resins, and the like are particularly preferably used.

The undercoat layer may contain a metal compound such as a silicon compound, an organic zirconium compound, an organic titanium compound, or an organic aluminum compound.
The ratio between the metal compound and the binder resin is not particularly limited, and is preferably set within a range in which desired electrophotographic photoreceptor characteristics can be obtained.

  Resin particles may be added to the undercoat layer in order to adjust the surface roughness. Examples of the resin particles include silicone resin particles and cross-linked polymethyl methacrylate (PMMA) resin particles. The surface may be polished after forming the undercoat layer for adjusting the surface roughness. As a polishing method, buffing, sandblasting, wet honing, grinding, or the like is used.

Here, the structure of the undercoat layer is particularly preferably a structure containing at least a binder resin and conductive particles. The conductivity means that the volume resistivity is less than 10 ⁷ Ω · cm, for example.
Examples of the conductive particles include metal particles (particles such as aluminum, copper, nickel, and silver), conductive metal oxide particles (particles such as antimony oxide, indium oxide, tin oxide, and zinc oxide), and conductive substance particles. (Carbon fiber, carbon black, particles of graphite powder) and the like. Among these, conductive metal oxide particles are preferable. You may mix and use 2 or more types of electroconductive particle.
In addition, the conductive particles may be subjected to a surface treatment with a hydrophobizing agent (for example, a coupling agent) or the like to adjust the resistance.
For example, the content of the conductive particles is preferably 10% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 80% by mass or less with respect to the binder resin.

  In forming the undercoat layer, an undercoat layer forming coating solution in which the above components are added to a solvent is used. In addition, as a method of dispersing particles in the coating solution for forming the undercoat layer, a media dispersing machine such as a ball mill, a vibrating ball mill, an attritor, a sand mill, a horizontal sand mill, a stirring, an ultrasonic dispersing machine, a roll mill, a high-pressure homogenizer, etc. Medialess dispersers are used. Here, examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, and a penetration method in which a fine flow path is dispersed in a high-pressure state. .

  Examples of the method for applying the coating solution for forming the undercoat layer onto the conductive substrate include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating. It is done.

  The thickness of the undercoat layer is preferably 15 μm or more, and more preferably 20 μm or more and 50 μm or less.

  Here, although not shown, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer. As the binder resin used for the intermediate layer, acetal resins such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl In addition to polymer resins such as acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, melamine resin, zirconium, titanium, aluminum, manganese, silicon atom, etc. An organometallic compound containing These compounds may be used alone or as a mixture or polycondensate of a plurality of compounds. Among these, an organometallic compound containing zirconium or silicon is preferable.

  In forming the intermediate layer, a coating solution for forming an intermediate layer in which the above components are added to a solvent is used. As the coating method for forming the intermediate layer, usual methods such as a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, and a curtain coating method are used.

  The thickness of the intermediate layer is preferably set to a film thickness range of 0.1 μm or more and 3 μm or less, for example. Further, this intermediate layer may be used as an undercoat layer.

Next, the charge generation layer will be described.
The charge generation layer includes, for example, a charge generation material and a binder resin. Examples of such charge generating materials include phthalocyanine pigments such as metal-free phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine, and in particular, a Bragg angle (2θ ± 0.2 °) with respect to CuKα characteristic X-rays. A chlorogallium phthalocyanine crystal having strong diffraction peaks at least at 7.4 °, 16.6 °, 25.5 ° and 28.3 °, a Bragg angle (2θ ± 0.2 °) to CuKα characteristic X-ray of at least 7 Metal-free phthalocyanine crystals having strong diffraction peaks at .7 °, 9.3 °, 16.9 °, 17.5 °, 22.4 °, and 28.8 °, Bragg angle (2θ ± 0) with respect to CuKα characteristic X-rays .2 °) at least 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 ° Hydroxygallium phthalocyanine crystals having strong diffraction peaks at 25.1 ° and 28.3 °, Bragg angles (2θ ± 0.2 °) with respect to CuKα characteristic X-rays of at least 9.6 °, 24.1 ° and 27.2 A titanyl phthalocyanine crystal having a strong diffraction peak at 0 ° can be mentioned. In addition, examples of the charge generation material include quinone pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, anthrone pigments, quinacridone pigments, and the like. These charge generation materials may be used alone or in combination of two or more.

Examples of the binder resin constituting the charge generation layer include polycarbonate resin such as bisphenol A type or bisphenol Z type, acrylic resin, methacrylic resin, polyarylate resin, polyester resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile-styrene. Copolymer resin, acrylonitrile-butadiene copolymer, polyvinyl acetate resin, polyvinyl formal resin, polysulfone resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride Examples thereof include resins, silicone resins, phenol-formaldehyde resins, polyacrylamide resins, polyamide resins, poly-N-vinylcarbazole resins. These binder resins may be used alone or in combination of two or more.
The mixing ratio of the charge generating material and the binder resin is desirably in the range of 10: 1 to 1:10.

When forming the charge generation layer, a coating solution for forming a charge generation layer in which the above components are added to a solvent is used.
As a method for dispersing particles (for example, charge generation material) in the coating solution for forming the charge generation layer, a media dispersion machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, a horizontal sand mill, an agitation, an ultrasonic dispersion machine, a roll mill, etc. Medialess dispersers such as high-pressure homogenizers are used. Examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, and a penetration method in which a fine flow path is dispersed in a high-pressure state.

  Examples of the method for applying the charge generation layer forming coating liquid on the undercoat layer include dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating. It is done.

  The thickness of the charge generation layer is desirably set in the range of 0.01 μm to 5 μm, more desirably 0.05 μm to 2.0 μm.

Next, the charge transport layer will be described.
The charge transport layer includes, for example, a charge transport material represented by the following general formula (1), a structural unit represented by the following general formula (2), and a structural unit represented by the following general formula (3). It comprises a polycarbonate resin, a compound represented by the following general formula (4), and a compound represented by the following general formula (5).

The charge transport material will be described.
The charge transport material is a charge transport material represented by the following general formula (1).

In General Formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 or more carbon atoms. It represents an alkoxy group having 20 or less, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure.
n and m each independently represent 0, 1 or 2.

In the general formula (1), examples of the halogen atom represented by R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ include fluorine, chlorine, bromine, iodine, etc. Among these, fluorine, chlorine Is desirable.

In general formula (1), examples of the alkyl group represented by R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ include a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, and an octadecyl group. And a branched chain such as isopropyl group and t-butyl group. Among these, those having a relatively low molecular weight such as methyl group, ethyl group, and isopropyl group are preferable.

In the general formula (1), examples of the alkoxy group represented by R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ include a methoxy group and an ethoxy group, and among these, a methoxy group is desirable.

In the general formula (1), examples of the aryl group represented by R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ include a phenyl group, a naphthyl group, a phenanthryl group, and a biphenylyl group. Of these, a phenyl group and a naphthyl group are preferable.

Note that each of the substituents represented by R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ may further have a substituent, and examples of the substituent include the halogen atoms exemplified above. And an alkoxy group, an alkyl group, and an aryl group.

In the general formula (1), a group connecting the substituents in a hydrocarbon ring structure in which two adjacent substituents of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are connected to each other. Examples thereof include a single bond, 2,2′-methylene group, 2,2′-ethylene group, 2,2′-vinylene group, and among these, a single bond and 2,2′-methylene group are desirable.

In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are preferably a hydrogen atom or a methyl group among the above.

  Specific examples of the charge transport material represented by the general formula (1) are shown below, but are not limited thereto.

  The content of the charge transport material represented by the general formula (1) is, for example, preferably 5% by mass or more and 45% by mass or less, and preferably 10% by mass with respect to the total solid content of the outermost surface layer (charge transport layer). It is 40 mass% or less.

In addition to the charge transport material represented by the general formula (1), other charge transport materials may be used in combination.
Examples of other charge transporting materials include oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1 -[Pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline and other pyrazoline derivatives, triphenylamine, N, N'-bis (3,4-dimethylphenyl) Aromatic tertiary amino compounds such as biphenyl-4-amine, tri (p-methylphenyl) aminyl-4-amine, dibenzylaniline, N, N'-bis (3-methylphenyl) -N, N'- Aromatic tertiary diamino compounds such as diphenylbenzidine, 3- (4′-dimethylaminophenyl) -5,6-di- (4′-methoxyphenyl) -1,2 1,2,4-triazine derivatives such as 4-triazine, hydrazone derivatives such as 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, 6-hydroxy-2, Benzofuran derivatives such as 3-di (p-methoxyphenyl) benzofuran, α-stilbene derivatives such as p- (2,2-diphenylvinyl) -N, N-diphenylaniline, enamine derivatives, carbazole derivatives such as N-ethylcarbazole , Hole transport materials such as poly-N-vinylcarbazole and its derivatives, quinone compounds such as chloranil and broanthraquinone, tetraanoquinodimethane compounds, 2,4,7-trinitrofluorenone, 2,4,5 , 7-tetranitro-9-fluorenone, etc. Examples thereof include electron transport materials such as non-compounds, xanthone compounds, thiophene compounds, and polymers having groups composed of the above-described compounds in the main chain or side chain. These other charge transport materials may be used alone or in combination of two or more.
Here, from the viewpoint of improving compatibility with the charge transport material and the polycarbonate resin, it is preferable to use the charge transport material represented by the general formula (1) and another binder resin in combination. In that case, the blending ratio (mass ratio) of the charge transport material represented by the general formula (1) and the other binder resin is preferably, for example, 1: 5 to 5: 1.

The polycarbonate resin will be described.
The polycarbonate resin is a polycarbonate resin comprising a structural unit (repeating unit) represented by the following general formula (2) and a structural unit (repeating unit) represented by the following general formula (3). (Referred to as polycarbonate resin).

In General Formula (2), R ⁷ and R ⁸ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or 6 or more carbon atoms. 12 or less aryl groups are represented.

In General Formula (3), R ⁹ and R ¹⁰ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or 6 or more carbon atoms. 12 or less aryl groups are represented.
X is —CR ¹¹ R ¹² — (wherein R ¹¹ and R ¹² are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms) Or a 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, —O—, —S—, —SO—, or -SO ₂ - represents a.

In general formula (2) and general formula (3), R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ are each independently preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. A methyl group is more desirable.
In the general formula (2), ^{X, -CR} 11 ^{R 12} -, preferably having 5 to 11 of 1,1-cycloalkylene group ^{carbon, -CR} 11 ^{R 12} - is more desirable. R ¹¹ and R ¹² in the —CR ¹¹ R ¹² — are each independently preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and among them, a methyl group or a phenyl group Is more preferable.

As a viscosity average molecular weight of specific polycarbonate resin, the range of 20,000 or more and 80,000 or less is good, for example.
In addition, as a measuring method of a viscosity average molecular weight, the following method is mentioned, for example. Specifically, for example, 1 g of resin is uniformly dissolved in 100 cm ³ of methylene chloride, and its specific viscosity ηsp is measured with an Ubbelohde viscometer under a measurement environment of 25 ° C., and ηsp / c = [η] +0.45 [ η] ² c (where c is the intrinsic viscosity [η] (cm ³ / g) from the concentration (g / cm ³ ) and is given by H. Schnell, [η] = 1.23 A one-point measuring method for determining the viscosity average molecular weight Mv from the relational expression of × 10 ⁻⁴ Mv ^0.83 is used.

  The specific polycarbonate resin uses, for example, a 4,4′-dihydroxybiphenyl compound represented by the following general formula (2A) and a bisphenol compound represented by the following general formula (3A) as raw materials to form carbonate esters such as phosgene. It can be obtained by a method such as polycondensation with a functional compound or transesterification with a bisaryl carbonate.

In general formulas (2A) and (3A), R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are the same as those in general formulas (2) and (3).

  Here, specific examples of the 4,4′-dihydroxybiphenyl compound represented by the general formula (2A) include 4,4′-dihydroxybiphenyl and 4,4′-dihydroxy-3,3′-dimethylbiphenyl. 4,4'-dihydroxy-2,2'-dimethylbiphenyl, 4,4'-dihydroxy-3,3'-dicyclohexylbiphenyl, 3,3'-difluoro-4,4'-dihydroxybiphenyl, 4,4 ' -Dihydroxy-3,3'-diphenylbiphenyl and the like.

  On the other hand, specific examples of the bisphenol compound represented by the general formula (3A) include, for example, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, and 1,2-bis (4 -Hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (3-methyl-4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) butane, 2 , 2-bis (4-hydroxyphenyl) octane, 4,4-bis (4-hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl) -1,1-diphenylmethane, 1,1-bis (4 -Hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) -1-phenylmethane, bis (4-hydroxyphenyl) ) Ether, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) cyclopentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2, 2-bis (3-methyl-4-hydroxyphenyl) propane, 2- (3-methyl-4-hydroxyphenyl) -2- (4-hydroxyphenyl) -1-phenylethane, bis (3-methyl-4- Hydroxyphenyl) sulfide, bis (3-methyl-4-hydroxyphenyl) sulfone, bis (3-methyl-4-hydroxyphenyl) methane, 1,1-bis (3-methyl-4-hydroxyphenyl) cyclohexane, 2, 2-bis (2-methyl-4-hydroxyphenyl) propane, 1,1-bis (2-butyl) 4-hydroxy-5-methylphenyl) butane, 1,1-bis (2-tert-butyl-4-hydroxy-3-methylphenyl) ethane, 1,1-bis (2-tert-butyl-4-hydroxy-) 5-methylphenyl) propane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) butane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) ) Isobutane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) heptane, 1,1-bis (2-tert-butyl-4-hydroxy-5-methylphenyl) -1- Phenylmethane, 1,1-bis (2-tert-amyl-4-hydroxy-5-methylphenyl) butane, bis (3-chloro-4-hydroxyphenyl) ) Methane, bis (3,5-dibromo-4-hydroxyphenyl) methane, 2,2-bis (3-chloro-4-hydroxyphenyl) propane, 2,2-bis (3-fluoro-4-hydroxyphenyl) Propane, 2,2-bis (3-bromo-4-hydroxyphenyl) propane, 2,2-bis (3,5-difluoro-4-hydroxyphenyl) propane, 2,2-bis (3,5-dichloro- 4-hydroxyphenyl) propane, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane, 2,2-bis (3-bromo-4-hydroxy-5-chlorophenyl) propane, 2,2- Bis (3,5-dichloro-4-hydroxyphenyl) butane, 2,2-bis (3,5-dibromo-4-hydroxyphenyl) butane, 1-phenyl-1, - bis (3-fluoro-4-hydroxyphenyl) ethane, bis (3-fluoro-4-hydroxyphenyl) ether, 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane. These bisphenol compounds may be used alone or in combination.

The specific polycarbonate resin has a content ratio of the structural unit represented by the general formula (2) in a molar ratio with respect to the total of the structural units represented by the general formulas (2) and (3). .9 or less, preferably 0.1 or more and 0.5 or less, more preferably 0.15 or more and 0.4 or less.
When the molar ratio of the structural unit represented by the general formula (2) is less than 0.05, the electronic photosensitive member is cracked or functioned due to contact with a contact-type charging unit due to long-term storage and use. Failures are likely to occur and image defects may occur. On the other hand, when the molar ratio exceeds 0.9, crystallization may easily occur in a part of the polycarbonate resin.

  The specific polycarbonate resin may include other structural units (other repeating units) than the structural units represented by the general formulas (2) and (3). In this case, the other structural unit (repeating unit) is preferably 0.03 or less, for example, in a molar ratio with respect to the entire structural unit (repeating unit) constituting the specific polycarbonate resin.

  Specific examples of the specific polycarbonate resin include the following, but are not limited thereto. In specific examples, m and n represent copolymerization ratios.

  In addition, a binder resin other than the specific polycarbonate resin may be used in combination as long as the function is not impaired. Examples of the other binder resin include polycarbonate resin such as bisphenol A type or bisphenol Z type, acrylic resin, methacrylic resin, polyarylate resin, polyester resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile-styrene copolymer. Resin, acrylonitrile-butadiene copolymer resin, polyvinyl acetate resin, polyvinyl formal resin, polysulfone resin, styrene-butadiene copolymer resin, vinylidene chloride-acrylonitrile copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride resin, Insulating resins such as silicone resin, phenol-formaldehyde resin, polyacrylamide resin, polyamide resin, chlorinated rubber, and polyvinylcarbazole, polyvinylanthracene, polyvinyl chloride Organic photoconductive polymers such as Rupiren like. These other binder resins may be used alone or in combination of two or more.

Here, the specific polycarbonate resin may be, for example, 10% by mass or more and 90% by mass or less, and preferably 30% by mass or more and 90% by mass or less, with respect to the total solid content of the outermost surface layer (charge transport layer). Desirably, it is 50 mass% or more and 90 mass% or less.
Also. The blending ratio (mass ratio) of the charge transport material and the above binder resin (specific polycarbonate resin + other binder resin) is desirably 10: 1 to 1: 5.

  The compounds represented by the general formulas (4) and (5) will be described.

In General Formula (4), R ²¹ , R ²² , and R ²³ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

In the general formula (4), examples of the alkyl group represented by R ²¹ and R ²² include straight-chain groups such as methyl group, ethyl group, propyl group, butyl group, octyl group, and octadecyl group, isopropyl group, t Examples include branched alkyl groups such as -butyl group, and bulky alkyl groups such as t-butyl group are particularly desirable.

In the general formula (4), examples of the alkyl group represented by R ²³ include straight-chain groups such as a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, and an octadecyl group, an isopropyl group, and a t-butyl group. And a branched alkyl group such as a methyl group or an ethyl group is preferable.
The alkyl group R ²³ is represented, for example, a methyl group is particularly desirable.

In the general formula (5), R ³¹ and R ³² each independently represents an alkyl group having 1 to 20 carbon atoms, specifically, for example, methyl group, ethyl group, propyl group, butyl group, octyl group Represents a linear alkyl group such as an octadecyl group, or a branched alkyl group such as an isopropyl group or a t-butyl group.
R ³³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, specifically, for example, a straight chain such as a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, an octadecyl group, Represents a branched alkyl group such as isopropyl group and t-butyl group.
R ³⁴ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aromatic group. Specifically, for example, a straight chain such as a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, or an octadecyl group. It represents a chain, a branched alkyl group such as isopropyl group or t-butyl group, or an aromatic group such as phenyl group or naphthyl group.
R ³⁵ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, specifically, for example, a straight chain such as a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, an octadecyl group, Represents a branched alkyl group such as isopropyl group and t-butyl group.
R ³⁶ and R ³⁷ each independently represent an alkyl group having 1 to 20 carbon atoms, specifically, for example, a straight chain such as a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, or an octadecyl group. Or a branched alkyl group such as isopropyl group and t-butyl group.

In the general formula (5), examples of the alkyl group represented by R ³¹ and R ³² include a methyl group and an ethyl group, and an ethyl group is desirable.

In the general formula (5), preferred examples of the alkyl group represented by R ³³ include a methyl group, an ethyl group, and a propyl group, and a methyl group is desirable.

In the general formula (5), the aromatic group represented by R ³⁴ is preferably a phenyl group.
In the general formula (5), examples of the alkyl group represented by R ³⁴ include a methyl group and an ethyl group, and a methyl group is preferable.

In the general formula (5), preferred examples of the alkyl group represented by R ³⁵ include a methyl group, an ethyl group, and a propyl group, and a methyl group is desirable.

In the general formula (5), examples of the alkyl group represented by R ³⁶ and R ³⁷ include a methyl group and an ethyl group, and an ethyl group is desirable.

  Specific examples of the compounds represented by the general formulas (4) and (5) include hindered phenol, hindered amine, paraphenylenediamine, and the like. More specifically, for example, 2,6-di- t-butyl-P-cresol, 4,4′-butylidenebis- (6-tert-butyl-3-methylphenol), 2,2′-methylenebis- (4-methyl-6-tert-butylphenol), 2,2 '-Methylenebis- (4-ethyl-6-t-butylphenol), 2,6-di-t-butyl-4-ethylphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-t -Butylphenyl) butane, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, P, P'-diaminodiphenylmethane, N-phenyl α-naphthylamine, N-phenyl-β-naphthylamine, P, P′-dimethoxydiphenylamine, N, N′-diphenyl-P-phenylenediamine, N, N′-di (β-naphthyl) -P-phenylenediamine, N -Cyclohexyl-N'-phenyl-P-phenylenediamine and the like.

Here, the compound represented by the general formula (4) may be 0.1% by mass or more and 10% by mass or less, and preferably 1% by mass with respect to the total solid content of the outermost surface layer (charge transport layer). % To 8% by mass, desirably 1% to 5% by mass.
On the other hand, the compound represented by the general formula (5) may be, for example, 0.1% by mass to 10% by mass with respect to the total solid content of the outermost surface layer (charge transport layer), preferably 0.5%. The content is from 5% by mass to 5% by mass, desirably from 1% by mass to 3% by mass.

Other additives will be described.
The charge transport layer may contain fluororesin particles.
Examples of the fluororesin particles include a tetrafluoroethylene resin, a trifluoroethylene chloride resin, a hexafluoropropylene resin, a vinyl fluoride resin, a vinylidene fluoride resin, a difluorodiethylene chloride resin, and copolymers thereof. It is desirable to select one or more of the particles. Among these, as the fluororesin particles, tetrafluoroethylene resin particles and vinylidene fluoride resin particles are particularly desirable.

The primary particle size of the fluororesin particles is preferably 0.05 μm or more and 1 μm or less, and preferably 0.1 μm or more and 0.5 μm or less.
The primary particles are obtained by obtaining a sample piece from the outermost surface layer of the electrophotographic photosensitive member, and observing this with a SEM (scanning electron microscope), for example, at a magnification of 5000 times or more. The diameter is measured and this is taken as the average value obtained for 50 particles. Note that a JSM-6700F manufactured by JEOL Ltd. is used as the SEM, and a secondary electron image with an acceleration voltage of 5 kV is observed.

  The fluororesin particles are preferably used in combination with a fluorine-based graft polymer as a dispersant. The amount of the dispersant is not particularly limited, but is preferably 0.1% by mass or more and 10% by mass or less with respect to the fluororesin particles.

  The content of the fluororesin particles is desirably 2% by mass or more and 15% by mass or less, and more desirably 4% by mass or more and 12% by mass or less with respect to the total solid content of the charge transport layer (outermost surface layer). More preferably, it is 6 mass% or more and 10 mass% or less.

The charge transport layer may further contain a fluorine-modified silicone oil as necessary. Examples of the fluorine-modified silicone oil include fluorine-modified silicone oil in which a part or all of the substituents of the organopolysiloxane are substituted with a fluoroalkyl group (for example, a fluoroalkyl group having 1 to 10 carbon atoms).
The content of the fluorine-modified silicone oil is, for example, preferably in the range of 0.1 ppm to 1000 ppm, and preferably in the range of 0.5 ppm to 500 ppm.

The charge transport layer is formed using a charge transport layer forming coating solution in which the above components are added to a solvent. As a method for dispersing particles (for example, fluororesin particles) in the coating liquid for forming the charge transport layer, a media dispersing machine such as a ball mill, a vibrating ball mill, an attritor, a sand mill, a horizontal sand mill, a stirring, an ultrasonic dispersing machine, a roll mill, etc. Medialess dispersers such as high-pressure homogenizers are used. Examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, and a penetration method in which a fine flow path is dispersed in a high-pressure state.
For example, when fluorine resin particles are dispersed in the charge transport layer forming coating solution, that is, when fluorine resin particles are included in the charge transport layer, a fluorosurfactant or fluorine-based surfactant is used as a dispersion stabilizer for the fluororesin particles. It is preferable to use a graft polymer in combination. Examples of the fluorine-based graft polymer include a macromonomer composed of an acrylic ester compound, a methacrylic ester compound, a styrene compound, and a resin graft-polymerized from perfluoroalkylethyl methacrylate.
The content of the fluorosurfactant or the fluorograft polymer is preferably, for example, from 1% by mass to 5% by mass with respect to the fluororesin particles.

  As a method for applying the charge transport layer forming coating solution on the charge generation layer, dip coating method, push-up coating method, wire bar coating method, spray coating method, blade coating method, knife coating method, curtain coating method, etc. The method is used.

  The film thickness of the charge transport layer is preferably 25 μm or more as described above, but may be, for example, 5 μm or more and less than 25 μm.

Next, the single layer type photosensitive layer will be described.
The single-layer type photosensitive layer is represented by, for example, a charge generation material, a charge transport material represented by the general formula (1), a structural unit represented by the general formula (2), and the following general formula (3). It is comprised including the polycarbonate resin comprised including a structural unit, the compound represented by General formula (4), and the compound represented by General formula (5).

The content of the charge generating material in the single-layer type photosensitive layer is about 10% by mass to 85% by mass, desirably 20% by mass to 50% by mass. In addition, the content of the charge transport material is desirably 5% by mass or more and 50% by mass or less.
The film thickness of the single-layer photosensitive layer is preferably 25 μm or more as described above, but may be, for example, 5 μm or more and less than 25 μm.

  Each layer constituting the photosensitive layer may contain additives such as a light stabilizer and a heat stabilizer. For example, as an antioxidant, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, an organic sulfur compound, an organic phosphorus compound, and the like can be given. Examples of the light stabilizer include derivatives such as benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine.

Further, each layer constituting the photosensitive layer may contain at least one electron accepting substance. Examples of the electron acceptor include succinic anhydride, maleic anhydride, dibromomaleic anhydride, phthalic anhydride, tetrabromophthalic anhydride, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrobenzene, m-dinitrobenzene, Examples include chloranil, dinitroanthraquinone, trinitrofluorenone, picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, and phthalic acid. Of these, benzene derivatives having an electron-withdrawing substituent such as fluorenone, quinone, Cl, CN, and NO ₂ are particularly desirable.

  The electrophotographic photosensitive member may have a configuration in which a protective layer is separately provided on the photosensitive layer. In this embodiment, the protective layer corresponds to the outermost surface layer and is represented by the general formula (1). A charge transport material, a polycarbonate resin comprising a structural unit represented by the general formula (2) and a structural unit represented by the following general formula (3), and a compound represented by the general formula (4): And a compound represented by the general formula (5).

[Image forming apparatus, etc.]
FIG. 3 is a schematic configuration diagram illustrating the image forming apparatus according to the present embodiment.
As shown in FIG. 3, the image forming apparatus 101 according to the present embodiment includes, for example, an electrophotographic photosensitive member 10 that rotates clockwise as indicated by an arrow a, and an electrophotographic photosensitive member 10 above the electrophotographic photosensitive member 10. A charging device 20 (an example of a charging unit) that is provided relative to the photographic photosensitive member 10 and charges the surface of the electrophotographic photosensitive member 10, and the surface of the electrophotographic photosensitive member 10 charged by the charging device 20 is exposed to light. An exposure device 30 (an example of an electrostatic latent image forming unit) that forms an electrostatic latent image, and a toner contained in a developer is attached to the electrostatic latent image formed by the exposure device 30 to form an electrophotographic photosensitive member 10. A developing device 40 (an example of a developing unit) that forms a toner image on the surface and a toner image formed on the surface of the electrophotographic photoreceptor 10 while traveling in the direction indicated by the arrow b while contacting the electrophotographic photoreceptor 10 Belt-like transfer And between transfer member 50, and a cleaning device 70 for cleaning the surface of the electrophotographic photosensitive member 10 (an example of a cleaning unit).

  The charging device 20, the exposure device 30, the developing device 40, the intermediate transfer member 50, the lubricant supply device 60, and the cleaning device 70 are arranged in a clockwise direction on the circumference surrounding the electrophotographic photosensitive member 10. In this embodiment, a mode in which the lubricant supply device 60 is disposed inside the cleaning device 70 will be described. However, the present invention is not limited to this, and the lubricant supply device 60 is disposed separately from the cleaning device 70. It may be in the form.

  The intermediate transfer member 50 is held from the inside while being tensioned by the support rollers 50A and 50B, the back roller 50C, and the drive roller 50D, and is driven in the direction of the arrow b as the drive roller 50D rotates. At a position facing the electrophotographic photosensitive member 10 inside the intermediate transfer member 50, the intermediate transfer member 50 is charged to a polarity different from the charging polarity of the toner, and the electrophotographic photosensitive member 10 is placed on the outer surface of the intermediate transfer member 50. A primary transfer device 51 for adsorbing the upper toner is provided. On the outer side below the intermediate transfer member 50, the recording paper P (an example of a recording medium) is charged to a polarity different from the charged polarity of the toner, and the toner image formed on the intermediate transfer member 50 is placed on the recording paper P. A secondary transfer device 52 for transferring is provided to face the back roller 50C. These members for transferring the toner image formed on the electrophotographic photosensitive member 10 to the recording paper P correspond to an example of a transfer unit.

  Below the intermediate transfer member 50, a recording paper supply device 53 that supplies the recording paper P to the secondary transfer device 52 and a recording paper P on which the toner image is formed in the secondary transfer device 52 are conveyed. A fixing device 80 for fixing the toner image is provided.

  The recording paper supply device 53 includes a pair of transport rollers 53A and a guide plate 53B that guides the recording paper P transported by the transport rollers 53A toward the secondary transfer device 52. On the other hand, the fixing device 80 includes a fixing roller 81 that is a pair of heat rollers for fixing the toner image by heating and pressing the recording paper P onto which the toner image has been transferred by the secondary transfer device 52, and a fixing roller. And a conveyance conveyor 82 that conveys the recording paper P toward 81.

  The recording paper P is conveyed in the direction indicated by the arrow c by the recording paper supply device 53, the secondary transfer device 52, and the fixing device 80.

  The intermediate transfer member 50 is further provided with an intermediate transfer member cleaning device 54 having a cleaning blade for removing the toner remaining on the intermediate transfer member 50 after the toner image is transferred to the recording paper P in the secondary transfer device 52. Yes.

  Details of main components in the image forming apparatus 101 according to the present embodiment will be described below.

(Charging device)
The charging device 20 is a contact type charging device that is brought into contact with the electrophotographic photosensitive member 10 and charges the surface of the electrophotographic photosensitive member 10 by applying a DC voltage.
The charging device 20 is composed of various known charging members such as a roller shape, a brush shape, and a film shape, and a roller-shaped charging member is particularly preferable. The roller-shaped charging member is preferably placed in contact with the electrophotographic photosensitive member 10 at a pressure of 250 mgf to 600 mgf, for example.
The charging device 20 applies, for example, a positive or negative DC voltage of 50 V or more and 2000 V or less (preferably 100 V or more and 1500 V or less) according to the required charging potential of the electrophotographic photoreceptor 10, It is better to be charged. An AC voltage may be superimposed as the voltage to be applied, but only a DC voltage is preferable from the viewpoint of suppressing the amount of wear (scraping amount) on the surface of the electrophotographic photosensitive member 10.

The roller-shaped charging member constituting the charging device 20 is a member made of a material adjusted to an electric resistance (10 ³ Ω or more and 10 ⁸ Ω or less) effective as a charging member. For example, the shaft and the outer peripheral surface of the shaft And a single layer or a plurality of elastic layers disposed on the surface.
These elastic layers include, for example, main materials (for example, urethane rubber, silicon rubber, fluorine rubber, chloroprene rubber, butadiene rubber, EPDM (ethylene-propylene-diene copolymer rubber), epichlorohydrin rubber and other synthetic rubber, polyolefin, polystyrene, An elastomer made of vinyl chloride or the like) and a conductivity imparting agent (for example, conductive carbon, metal oxide, ionic conductive agent, etc.) are blended.
The elastic layer is made from a resin (nylon, polyester, polystyrene, polyurethane, silicone, etc.), and a suitable amount of a conductivity-imparting agent (eg, conductive carbon, metal oxide, ionic conductive agent, etc.) is blended there. May be formed in a layer by any method such as dipping, spraying, roll coating, or the like.

  The charging device 20 may be charged by being rotated at the same peripheral speed of the electrophotographic photosensitive member 10 while being driven by the electrophotographic photosensitive member 10, or may be separately rotated by a driving unit to be electromotive photosensitive member 10. Charging may be performed by rotating at a peripheral speed different from that in FIG.

(Exposure equipment)
Examples of the exposure apparatus 30 include optical system devices that expose the surface of the electrophotographic photoreceptor 10 with light such as semiconductor laser light, LED light, and liquid crystal shutter light imagewise. The wavelength of the light source is preferably within the spectral sensitivity region of the electrophotographic photoreceptor 10. As the wavelength of the semiconductor laser, for example, near infrared having an oscillation wavelength around 780 nm is preferable. However, the present invention is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a laser having an oscillation wavelength of 400 nm to 450 nm as a blue laser may be used. Further, as the exposure apparatus 30, for example, a surface emitting laser light source of a multi-beam output type is also effective for color image formation.

(Developer)
The developing device 40 is disposed, for example, opposite to the electrophotographic photoreceptor 10 in the developing region, and includes, for example, a developing container 41 (developing device main body) that contains a two-component developer composed of toner and a carrier, and a replenishment device. A developer storage container (toner cartridge) 47. The developing container 41 includes a developing container main body 41A and a developing container cover 41B that closes the upper end thereof.

  The developing container main body 41A has, for example, a developing roll chamber 42A that accommodates the developing roll 42 therein, and is adjacent to the first stirring chamber 43A and the first stirring chamber 43A adjacent to the developing roll chamber 42A. Second agitating chamber 44A. Further, in the developing roll chamber 42A, for example, a layer thickness regulating member 45 for regulating the layer thickness of the developer on the surface of the developing roll 42 is provided when the developing container cover 41B is attached to the developing container main body 41A. Yes.

  The first stirring chamber 43A and the second stirring chamber 44A are partitioned by, for example, a partition wall 41C. Although not shown, the first stirring chamber 43A and the second stirring chamber 44A are arranged in the longitudinal direction of the partition wall 41C (developing device). (Longitudinal direction) Openings are provided at both ends, and the circulation stirring chamber (43A + 44A) is constituted by the first stirring chamber 43A and the second stirring chamber 44A.

  The developing roll 42 is disposed in the developing roll chamber 42 </ b> A so as to face the electrophotographic photoreceptor 10. Although not shown, the developing roll 42 is provided with a sleeve outside a magnetic roll (fixed magnet) having magnetism. The developer in the first stirring chamber 43A is adsorbed on the surface of the developing roll 42 by the magnetic force of the magnetic roll and is transported to the developing area. Further, the developing roller 42 has a roll shaft supported rotatably on the developing container main body 41A. Here, the developing roll 42 and the electrophotographic photoreceptor 10 rotate in the same direction, and the developer adsorbed on the surface of the developing roll 42 at the opposite portion is opposite to the traveling direction of the electrophotographic photoreceptor 10. It is conveyed from the direction to the development area.

  Further, a bias power source (not shown) is connected to the sleeve of the developing roll 42 so that a developing bias is applied (in this embodiment, a direct current component is applied so that an alternating electric field is applied to the developing region. (A bias in which an alternating current component (DC) is superimposed on (AC) is applied).

  In the first stirring chamber 43A and the second stirring chamber 44A, a first stirring member 43 (stirring / conveying member) and a second stirring member 44 (stirring / conveying member) that convey the developer while stirring are disposed. The first stirring member 43 includes a first rotating shaft that extends in the axial direction of the developing roll 42, and an agitating / conveying blade (protrusion) that is helically fixed to the outer periphery of the rotating shaft. Similarly, the second agitating member 44 includes a second rotating shaft and an agitating / conveying blade (protrusion). The stirring member is rotatably supported by the developing container main body 41A. The first stirring member 43 and the second stirring member 44 are arranged such that the developer in the first stirring chamber 43A and the second stirring chamber 44A is conveyed in the opposite directions by rotation thereof. .

  One end of a replenishment conveyance path 46 for supplying replenishment developer including replenishment toner and replenishment carrier to the second agitation chamber 44A is connected to one end side in the longitudinal direction of the second agitation chamber 44A. The other end of the replenishment conveyance path 46 is connected to a replenishment developer storage container 47 that contains a replenishment developer.

  In this manner, the developing device 40 supplies the replenishment developer from the replenishment developer storage container (toner cartridge) 47 to the development device 40 (second stirring chamber 44A) through the replenishment conveyance path 46.

Here, the developer used in the developing device 40 will be described.
As the developer, a two-component developer including a toner and a carrier is employed.

First, the toner will be described.
The toner includes, for example, toner particles containing a binder resin, a colorant, and, if necessary, other additives such as a release agent, and external additives as necessary.

The toner particles have an average shape factor (shape factor = (ML ² / A) × (π / 4) × 100), and ML represents the maximum length of the particles, where A represents the maximum length of the particles (Representing the projected area) is preferably from 100 to 150, more preferably from 105 to 145, and even more preferably from 110 to 140. Further, the toner preferably has a volume average particle diameter of 3 μm or more and 12 μm or less, more preferably 3.5 μm or more and 10 μm or less, and further preferably 4 μm or more and 9 μm or less.

  The toner particles are not particularly limited by the production method, and for example, a kneading and pulverizing method in which a binder resin, a colorant and a release agent, and a charge control agent and the like are added, if necessary, are kneaded, pulverized, and classified; A method of changing the shape of the particles obtained by the kneading and pulverization method by mechanical impact force or thermal energy; the polymerization monomer of the binder resin is emulsion-polymerized, the formed dispersion, the colorant and the release agent Emulsion polymerization aggregation method to obtain a toner particle by mixing a mold agent and, if necessary, a dispersion of a charge control agent, and agglomerating and heat-fusing; a polymerizable monomer for obtaining a binder resin, and coloring Suspension polymerization method in which a solution of an agent, a release agent and, if necessary, a charge control agent is suspended in an aqueous solvent for polymerization; a binder resin, a colorant and a release agent, and if necessary, a charge control agent Toner particles produced by a solution suspension method in which a solution such as a liquid is suspended in an aqueous solvent and granulated There will be used.

  Further, a known method such as a production method in which the toner particles obtained by the above method are used as a core, and agglomerated particles are further adhered and heated and fused to give a core-shell structure is used. The toner production method is preferably a suspension polymerization method, an emulsion polymerization aggregation method, or a dissolution suspension method in which an aqueous solvent is used from the viewpoint of shape control and particle size distribution control, and an emulsion polymerization aggregation method is particularly desirable.

  The toner is produced by mixing the toner particles and the external additive with a Henschel mixer or a V blender. Further, when the toner particles are produced by a wet method, they may be externally added by a wet method.

  On the other hand, as the carrier, iron powder, glass beads, ferrite powder, nickel powder, or the like coated with a resin is used. Further, the mixing ratio of the carrier and the toner is not particularly limited and is set within a known range.

(Transfer device)
Examples of the primary transfer device 51 and the secondary transfer device 52 include a contact transfer charger using a belt, a roller, a film, a rubber blade, and the like, a scorotron transfer charger using a corona discharge, a corotron transfer charger, and the like. A transfer charger known per se can be used.
The primary transfer device 51 may transfer a toner image to the intermediate transfer member 50 by applying a voltage having a polarity opposite to that of the toner to the toner image.

  As the intermediate transfer member 50, a belt-like member (intermediate transfer belt) such as polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber containing a conductive agent is used. Further, as the form of the intermediate transfer member, a cylindrical one is used in addition to the belt shape.

(Cleaning device)
The cleaning device 70 includes, for example, a housing 71, a cleaning blade 72 disposed so as to protrude from the housing 71, and a lubricant supply device disposed on the downstream side of the cleaning blade 72 in the rotation direction of the electrophotographic photosensitive member 10. 60.
The lubricant supply device 60 is provided, for example, inside the cleaning device 70 and upstream of the cleaning blade 72 in the rotation direction of the electrophotographic photosensitive member 10.
The lubricant supply device 60 includes, for example, a rotating brush 61 disposed in contact with the electrophotographic photosensitive member 10 and a solid lubricant 62 disposed in contact with the rotating brush 61. . In the lubricant supply device 60, the rotating brush 61 is rotated while being in contact with the solid lubricant 62, whereby the lubricant 62 adheres to the rotating brush 61, and the attached lubricant 62 becomes the electrophotographic photosensitive member. The film of the lubricant 62 is formed on the surface 10.
The lubricant supply device 60 is not limited to the above form, and may be a form that employs a rubber roller instead of the rotating brush 61, for example.
Examples of the lubricant 62 include metal soap and wax.

  Next, the operation of the image forming apparatus 101 according to the present embodiment will be described. First, the electrophotographic photoreceptor 10 rotates along the direction indicated by the arrow a, and at the same time is negatively charged by the charging device 20.

  The electrophotographic photoreceptor 10 whose surface is negatively charged by the charging device 20 is exposed by the exposure device 30, and a latent image is formed on the surface.

  When the portion where the latent image is formed on the electrophotographic photoreceptor 10 approaches the developing device 40, the developing device 40 (developing roll 42) attaches toner to the latent image and forms a toner image.

  When the electrophotographic photosensitive member 10 on which the toner image is formed further rotates in the direction of arrow a, the toner image is transferred to the outer surface of the intermediate transfer member 50.

  When the toner image is transferred to the intermediate transfer member 50, the recording paper P is supplied to the secondary transfer device 52 by the recording paper supply device 53, and the toner image transferred to the intermediate transfer member 50 is transferred by the secondary transfer device 52. Transferred onto the recording paper P. As a result, a toner image is formed on the recording paper P.

  The toner image is fixed on the recording paper P on which the image is formed by the fixing device 80.

  Here, after the toner image is transferred to the intermediate transfer member 50, the electrophotographic photosensitive member 10 is transferred, and then the lubricant supply device 60 supplies the lubricant 62 to the surface of the electrophotographic photosensitive member 10. A film of the lubricant 62 is formed on the surface of the photographic photoreceptor 10. Thereafter, the toner and discharge products remaining on the surface are removed by the cleaning blade 72 of the cleaning device 70. Then, the electrophotographic photosensitive member 10 from which the transfer residual toner and discharge products are removed in the cleaning device 70 is charged again by the charging device 20 and is exposed in the exposure device 30 to form a latent image.

Further, for example, as illustrated in FIG. 4, the image forming apparatus 101 according to the present embodiment includes an electrophotographic photosensitive member 10, a charging device 20, a developing device 40, a lubricant supply device 60, and a cleaning in a housing 11. A configuration including a process cartridge 101A that integrally accommodates the apparatus 70 may be employed. The process cartridge 101A integrally contains a plurality of members and is attached to and detached from the image forming apparatus 101. In the image forming apparatus 101 shown in FIG. 4, a form in which the replenishment developer storage container 47 is not provided in the developing device 40 is shown.
The configuration of the process cartridge 101A is not limited to this. For example, the process cartridge 101A only needs to include at least the electrophotographic photoreceptor 10 and the charging device 20, and for example, the exposure device 30, the developing device 40, the primary transfer device 51, and the like. At least one selected from the cleaning device 70 may be provided.

  Further, the image forming apparatus 101 according to the present embodiment is not limited to the above-described configuration, and may employ a known configuration, for example, a method of directly transferring a toner image formed on the electrophotographic photosensitive member 10 to the recording paper P. Alternatively, a tandem image forming apparatus may be employed.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention. Unless otherwise specified, all “parts” mean “parts by mass”.

Example 1
100 parts by mass of zinc oxide (average particle diameter: 70 nm, manufactured by Teica, specific surface area value: 15 m ² / g) is stirred and mixed with 500 parts by mass of methanol, and KBM603 (manufactured by Shin-Etsu Chemical Co., Ltd.) is used as a silane coupling agent. 25 parts by mass was added and stirred for 2 hours. Thereafter, methanol was distilled off under reduced pressure, and baking was performed at 120 ° C. for 3 hours to obtain silane coupling agent surface-treated zinc oxide particles.

60 parts by mass of surface-treated zinc oxide particles, 0.6 parts by mass of alizarin, 13.5 parts by mass of blocked isocyanate (Sumidule 3173, manufactured by Sumitomo Bayern Urethane Co., Ltd.) as a curing agent, and butyral resin (BM- (1; manufactured by Sekisui Chemical Co., Ltd.) 15 parts by mass of 38 parts by mass of a solution obtained by dissolving 85 parts by mass of methyl ethyl ketone and 25 parts by mass of methyl ethyl ketone are mixed and dispersed for 4 hours in a sand mill using glass beads having a diameter of 1 mm. To obtain a dispersion. To the obtained dispersion, 0.005 parts by mass of dioctyltin dilaurate and 4.0 parts by mass of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicone) are added as a catalyst to obtain an undercoat layer coating solution. It was.
This coating solution was applied on an aluminum substrate having a diameter of 30 mm by a dip coating method, followed by drying and curing at 180 ° C. for 40 minutes to obtain an undercoat layer having a thickness of 25 μm.

  Next, as a charge generation material, it has strong diffraction peaks at Bragg angles (2θ ± 0.2 °) with respect to CuKα characteristic X-rays of at least 7.4 °, 16.6 °, 25.5 ° and 28.3 °. Using a glass bead having a diameter of 1 mm, a mixture of 15 parts by weight of chlorogallium phthalocyanine crystal, 10 parts by weight of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Union Carbide) and 300 parts by weight of n-butyl alcohol was used. Then, it was dispersed in a sand mill for 4 hours to obtain a coating solution for the charge generation layer. This charge generation layer coating solution was dip coated on the undercoat layer and dried to obtain a charge generation layer having a thickness of 0.2 μm.

  Next, 0.6 parts by mass of tetrafluoroethylene resin particles (average particle size: 0.2 μm) and 0.015 parts by mass of fluorinated alkyl group-containing methacrylic copolymer (weight average molecular weight: 30,000) were added to tetrahydrofuran 4 The mixture was kept at a liquid temperature of 20 ° C. together with 1 part by mass of toluene and 1 part by mass of toluene and stirred for 48 hours to obtain a tetrafluoroethylene resin particle suspension.

  Next, as a charge transport material represented by the general formula (1), 1 part by mass of a charge transport material represented by the following exemplary compound 1-1, and represented by the following compound 1-B as another charge transport material. As a polycarbonate resin (binder resin) having a structural unit represented by 3 parts by mass of the charge transport material and the general formulas (2) and (3), a polycarbonate resin (m: n = 0.2: 0.8) 6 parts by mass, as a compound represented by the general formula (4), 2,6-di-t-butyl-4-methylphenol 0.1 parts by mass, in the general formula (5) As a compound represented, 0.1 part by mass of bis (4-diethylamino-2-methylphenyl) -phenylmethane was mixed and dissolved in 24 parts by mass of tetrahydrofuran and 11 parts by mass of toluene to obtain a mixed solution.

Next, a suspension obtained by adding the above tetrafluoroethylene resin particle suspension and stirring and mixing the obtained mixed solution to a high-pressure homogenizer (Yoshida Kikai Co., Ltd.) equipped with a through-type chamber having fine flow paths. 5 ppm of fluorine-modified silicone oil (trade name: FL-100 manufactured by Shin-Etsu Silicone Co., Ltd.) is added to the solution obtained by repeating the dispersion treatment by increasing the pressure up to 500 kgf / cm <2> six times. Thus, a coating liquid for forming a charge transport layer was obtained.
This coating solution for forming a charge transport layer was applied onto the charge generation layer and dried at 135 ° C. for 30 minutes to form a charge transport layer having a thickness of 20 μm to obtain an electrophotographic photoreceptor.

(Examples 2 to 12)
Composition of charge transport layer, charge transport material represented by general formula (1), other charge transport material, polycarbonate resin having structural units represented by general formulas (2) and (3), general formula Except that the compound represented by (4), the type and amount of the compound represented by formula (5), and the film thickness of the charge transport layer were changed according to Tables 1 to 3, the same as in Example 1. Thus, an electrophotographic photosensitive member was obtained.

(Comparative Examples 1-8)
Composition of charge transport layer, charge transport material represented by general formula (1), other charge transport material, polycarbonate resin having structural units represented by general formulas (2) and (3), general formula Except that the compound represented by (4), the type and amount of the compound represented by formula (5), and the film thickness of the charge transport layer were changed according to Tables 1 to 3, the same as in Example 1. Thus, an electrophotographic photosensitive member was obtained.

(Evaluation)
The electrophotographic photoreceptor obtained in each example was stored overnight at 28 ° C. and 85% RH, and then in an environment of 28 ° C. and 85% RH, DocuPrint C1100 (manufactured by Fuji Xerox Co., Ltd .: with neutralizer: photoreceptor charged) Method = charging roll is brought into contact with the photosensitive member at 800 gf (7.85 N) and incorporated in a method of charging by applying a DC voltage of -400 V), and a halftone image (intermediate gradation image: image density 20%) is printed. The streak-like image defect in the photoconductor axis direction was determined according to the following evaluation criteria.
Thereafter, in an environment of 28 ° C. and 85% RH. Incorporated into a modified DocuPrint C1100 machine with the static eliminator removed, a halftone image (intermediate tone image: image density 20%) was printed in the same manner, and a streak image defect in the direction of the photoconductor axis was determined according to the following evaluation criteria. .
-Evaluation criteria-
A: Level that does not occur at all B: Occurrence that is much slower than C (level that is hardly noticed but occurs when you look closely)
C: Generated slightly more than D D: Generated clearly but not on the entire surface E: Generated on the entire surface Clearly

  In Tables 1 and 2, Me represents a methyl group, t-Bu represents a t-butyl group, Et represents an ethyl group, and Ph represents a phenyl group.

From the above results, it can be seen that, in this embodiment, streak-like image defects in the photosensitive member axial direction are suppressed as compared with the comparative example.
Further, in this embodiment, it can be seen that streak-like image defects in the axial direction of the photosensitive member are suppressed even when mounted on a device that does not have a static eliminator as compared with the comparative example.

DESCRIPTION OF SYMBOLS 1 Undercoat layer, 2 Charge generation layer, 3 Charge transport layer, 4 Conductive substrate, 6 Single layer type photosensitive layer, 10 Electrophotographic photoreceptor, 10A Electrophotographic photoreceptor, 10B Electrophotographic photoreceptor, 20 Charging device, 30 Exposure device, 40 developing device, 41 developing container, 41A developing container body, 41B developing container cover, 41C wall, 42 developing roll, 42A developing roll chamber, 43 stirring member, 43A stirring chamber, 44 stirring member, 44A stirring chamber, 45 Layer thickness regulating member, 46 Supply transport path, 47 Supply developer container, 50 Intermediate transfer member, 50A Support roller, 50B Support roller, 50C Back roller, 50D Drive roller, 51 Primary transfer device, 52 Secondary transfer device, 53 Recording paper supply device, 53A conveying roller, 53B guide plate, 54 intermediate transfer member cleaning device, 70 cleaning Location, 71 housing, 72 cleaning blade, 80 a fixing device, 81 a fixing roller, 82 conveyor, 101 an image forming apparatus, 101A process cartridge

Claims (6)

Having at least a conductive substrate and a photosensitive layer disposed on the conductive substrate,
The outermost surface layer includes at least a charge transport material represented by the following general formula (1), a structural unit represented by the following general formula (2), and a structural unit represented by the following general formula (3). An electrophotographic photoreceptor comprising a polycarbonate resin, a compound represented by the following general formula (4), and a compound represented by the following general formula (5).

(In General Formula (1), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 carbon atom. It represents an alkoxy group having 20 or less or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and two adjacent substituents may be bonded to form a hydrocarbon ring structure. m represents 0, 1 or 2 each independently.)
(In General Formula (2), R ⁷ and R ⁸ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or 6 carbon atoms. Represents an aryl group of 12 or less.)
(In General Formula (3), R ⁹ and R ¹⁰ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or 6 carbon atoms. Represents an aryl group having at least 12 but X is —CR ¹¹ R ¹² — (wherein R ¹¹ and R ¹² are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or Represents an aryl group having 6 to 12 carbon atoms), a 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, —O—, -S -, - SO-, or -SO ₂ - represents a).
(In General Formula (4), R ²¹ , R ²² , and R ²³ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.)
(In General Formula (5), R ³¹ and R ³² each independently represents an alkyl group having 1 to 20 carbon atoms. R ³³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. R ³⁴ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aromatic group, R ³⁵ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, R ³⁶ And R ³⁷ each independently represents an alkyl group having 1 to 20 carbon atoms.   The electrophotographic photosensitive member according to claim 1, wherein the outermost surface layer has a thickness of 25 μm or more. The electrophotographic photosensitive member according to claim 1 or 2,
Contact-type charging means for charging the electrophotographic photosensitive member by application of a DC voltage; and
Comprising at least
A process cartridge that is detachable from the image forming apparatus.   The process cartridge according to claim 3, wherein the process cartridge does not have a charge removing unit for discharging charges on the electrophotographic photosensitive member after the toner image is transferred to the transfer target and before the electrophotographic photosensitive member is charged. The electrophotographic photosensitive member according to claim 1 or 2,
Contact-type charging means for charging the electrophotographic photosensitive member by application of a DC voltage; and
Electrostatic latent image forming means for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image; and
Toner image forming means for developing the electrostatic latent image formed on the electrophotographic photosensitive member with a developer containing toner to form a toner image;
Transfer means for transferring a toner image formed on the electrophotographic photosensitive member to a transfer target;
Fixing means for fixing the toner image transferred to the transfer target;
An image forming apparatus.   6. The image formation according to claim 5, wherein the toner image is not provided with a discharging unit for discharging charges on the electrophotographic photosensitive member after the toner image is transferred to the transfer target and before the electrophotographic photosensitive member is charged. apparatus.